Some Accessory Factors in Plant Grotvth and Nutrition. 243 



Table IV. 



Series. 



Weight of 30 plants. 



Increase over Series I. 



I. Complete food solution 



II. „ „ „ + alcoholic extract 

 III. „ „ „ + phospliotungstic 

 fraction 



grm. 

 11 -94 

 14-46 

 15 -45 



per cent. 



21-1 

 29 -4 



The results thus obtained indicate that the stimulative substance in 

 bacterised peat is precipitated by phosphotungstic acid, and that this 

 phosphotungstic fraction is quite as effective as the original alcoholic extract 

 of the peat. Funk* found that, upon further fractionation of his phospho- 

 tungstic acid precipitate with silver nitrate and baryta and. elimination of 

 the reagents, he obtained a relatively pure crystalline substance, to which he 

 gave the name " vitamine," and this he considered to be the specific curative 

 substance. In order to determine how far the growth stimulant in bacterised 

 peat resembled these so-called " vitamines," a further fractionation was 

 carried out along the lines described in his paper. The phosphotungstic 

 acid precipitate was decomposed, as before described, with baryta, and the 

 last traces of baryta eliminated by means of sulphuric acid. To the' filtrate 

 from the barium salt silver nitrate was first added, and then baryta, until no 

 further precipitate was produced. The brownish precipitate was filtered off, 

 well washed, suspended in dilute sulphuric acid, and decomposed with 

 sulphuretted hydrogen. The filtrate from the silver sulphide was then 

 exactly neutralised with baryta, the clear liquid filtered off from the 

 precipitate of barium sulphate, and evaporated to dryness in vacuo. The 

 weight of dry substance obtained from the silver fraction from 7 kgrm. of 

 bacterised peat amounted to 0*2452 grm., and, since this also was made up 

 for experiment into a solution containing the silver fraction from 10 grm. of 

 peat per litre, this solution contained the dry substance from the silver 

 fraction in the proportion of 0*35 part per million. This fraction was also 

 tested, concurrently with the phosphotungstic acid fraction, upon wheat 

 seedlings ; 15 seeds were germinated in clean sand in each of nine pots, 

 which were arranged in three series of three each. Series I was treated 

 with complete food solution, containing nitrogen, phosphorus, and potash, 

 estimated as NH 3 , P 2 5 , and K 2 0, in the proportion of 400, 200, and 1220 

 parts per million respectively. Series II was treated with a similar solution, 

 containing in addition 17 parts per million of the phosphotungstic fraction, 



* Funk, ' Journ. Physiol.,' vol. 45 (1912-1913). 



